1. Technical Field
This disclosure generally relates to a liquid crystal display device and a display apparatus including the liquid crystal display device.
2. Description of the Related Art
Twisted nematic liquid crystal display devices are widely used as a type of liquid crystal display device. Meanwhile, vertical alignment liquid crystal display devices having advantages in terms of viewing angle dependence and the contrast ratio are being actively developed. In a vertical alignment liquid crystal display device, liquid crystal molecules having a negative dielectric anisotropy are aligned perpendicular to a substrate and are driven parallel to the substrate by applying a voltage.
Patent documents 1 through 4 disclose methods of aligning liquid crystal molecules perpendicular to a substrate using a liquid crystal alignment film made of polyimide and formed on an indium tin oxide (ITO) layer on a glass substrate. In the disclosed methods, a vertical alignment film is formed by applying a solution of polyamic acid dissolved in an organic solvent to a substrate using, for example, a spinner, imidizing the polyamic acid by heating the solution at a temperature between 120° C. and 250° C., and rubbing the film of the solution using, for example, felt to give it a vertical alignment property.
Patent document 5 discloses a non-rubbing method of aligning liquid crystal molecules perpendicular to a substrate using a polyimide resin as a non-rubbing vertical alignment material. In this method, a vertical alignment film is formed by applying polyamic acid to a substrate by spinning, pre-calcining the substrate at 100° C. for 30 minutes, and imidizing the polyamic acid by calcining the substrate at 250° C. for an hour.
Patent document 6 discloses still another method of forming a vertical alignment film using a liquid crystal alignment agent comprising polyamic acid and having a conjugated enone structure. In this method, a solution of the alignment agent dissolved in an organic solvent is applied to a substrate using, for example, a spinner, the substrate is heated at a temperature between 150 and 250° C. to imidize the alignment agent, and then the film of the solution is irradiated by ultraviolet rays with a wavelength between 320 and 450 nm to give it a vertical alignment property.
[Patent document 1] Japanese Patent Application Publication No. 2001-305549
[Patent document 2] Japanese Patent Application Publication No. 2001-311080
[Patent document 3] Japanese Patent Application Publication No. 2002-323701
[Patent document 4] Japanese Patent Application Publication No. 2003-295194
[Patent document 5] Japanese Patent Application Publication No. 2006-516757
[Patent document 6] Japanese Patent Application Publication No. 2003-114437
However, with the above methods, it is difficult to form a uniform liquid crystal alignment film on an irregular surface of a substrate covered with thin-film transistors (TFTs) and wiring because it is difficult to evenly apply a solution to the substrate surface.
Also with the above methods, because the substrate is heated at a temperature between 120 and 250° C. after a solution is applied, it is not possible to use a versatile flexible plastic film as the substrate instead of a glass substrate.
Also, the vertical alignment property of a vertical alignment film given by a rubbing method tends to become uneven because it is difficult to evenly rub an irregular surface of the substrate, and accordingly, the uneven vertical alignment property disturbs the liquid crystal alignment.
Further, a rubbing method, where an alignment film is rubbed with a cloth, tends to generate static electricity and dust that may damage TFTs and cause a display defect.
BRIEF SUMMARY
In an aspect of this disclosure, there is provided a liquid crystal display device that embodies the present invention, as discussed infra, and a display apparatus including the liquid crystal display device.
In an embodiment, a liquid crystal display device includes a liquid crystal composition contained in a cell having a liquid crystal alignment film. The liquid crystal alignment film has a lamellar structure and includes at least one type of a triphenylene compound (I) represented by general formula (1):

wherein L represents —O— or —S—; R1, R2, R3, R4, and R5 represent the same or different hydrocarbon groups with 4 or more carbon atoms; R6 represents a divalent hydrocarbon radical with 4 or more carbon atoms; and R7 represents —SiR8R9R10 or —P(═O)(OH)2 where R8, R9, and R10 each individually represents —Cl, —OH, —OCH3, or —OC2H5.